Workflow to set approval status without stored credentials?

I'm replacing SharePoint Designer workflows with Nintex, and I have a custom content approval workflow that does content approval in an app step as the workflow initiator will not have approval permissions.

I'm converting it to Nintex and the only option available seems to be the action "Office 365 set approval status", which seems to be designed to run on any arbitrary Office 365 SharePoint library as it requires the site URL, list name, and list query to find the item to approve to be configured, as well as credentials stored in the action to access that environment.

Am I missing a straightforward "Set current item approval status" action that would not require credentials to run in the workflow context and could be used in an app step? Storing credentials is not an option - I have a service account used to publish the workflow but the password will be reset when I've completed this contract, and the workflow will be rolled out to dozens of libraries in different subsites. I could store the credentials in a list somewhere I guess but this seems unnecessarily convoluted.

Did you ever resolve this.. I'm in the process of migrating from Nintex onPremise, that has a set Approval status action, to Nintex Online that appears to need to use the generic O365 set approval, much more complex action...